Assessing age-related changes in peripheral blood leukocyte phenotypes in domestic shorthaired cats using flow cytometry

Antibody Responses in Cats Following Primary and Annual Vaccination against Feline Immunodeficiency Virus (FIV) with an Inactivated Whole-Virus Vaccine (Fel-O-Vax® FIV)

Although the antibody response induced by primary vaccination with Fel-O-Vax^® FIV (three doses, 2–4 weeks apart) is well described, the antibody response induced by annual vaccination with Fel-O-Vax^® FIV (single dose every 12 months after primary vaccination) and how it compares to the primary antibody response has not been studied. Residual blood samples from a primary FIV vaccination study (n = 11), and blood samples from cats given an annual FIV vaccination (n = 10), were utilized. Samples from all 21 cats were tested with a commercially available PCR assay (FIV RealPCR^TM), an anti-p24 microsphere immunoassay (MIA), an anti-FIV transmembrane (TM; gp40) peptide ELISA, and a range of commercially available point-of-care (PoC) FIV antibody kits. PCR testing confirmed all 21 cats to be FIV-uninfected for the duration of this study. Results from MIA and ELISA testing showed that both vaccination regimes induced significant antibody responses against p24 and gp40, and both anti-p24 and anti-gp40 antibodies were variably present 12 months after FIV vaccination. The magnitude of the antibody response against both p24 and gp40 was significantly higher in the primary FIV vaccination group than in the annual FIV vaccination group. The differences in prime versus recall post-vaccinal antibody levels correlated with FIV PoC kit performance. Two FIV PoC kits that detect antibodies against gp40, namely Witness^® and Anigen Rapid^®, showed 100% specificity in cats recently administered an annual FIV vaccination, demonstrating that they can be used to accurately distinguish vaccination and infection in annually vaccinated cats. A third FIV PoC kit, SNAP^® Combo, had 0% specificity in annually FIV-vaccinated cats, and should not be used in any cat with a possible history of FIV vaccination. This study outlines the antibody response to inactivated Fel-O-Vax^® FIV whole-virus vaccine, and demonstrates how best to diagnose FIV infection in jurisdictions where FIV vaccination is practiced.

The First Report of Immunoglobulin G, M, and A Concentrations in Serum of European Bison and Their Changes with Age

The age-specific reference values for immunoglobulin (Ig) serum concentrations in European bison (Bison bonasus) are lacking. Identification of immune alterations that accompany normal physiological aging will help assist in development of better monitoring health programs. In the present study, the age-associated changes in concentration of IgG, IgM, and IgA in serum of apparently healthy European bison of various ages were studied. The quantities of IgA, IgM, and IgG were measured by the use of a commercial ELISA kit. The serum samples originating from apparently healthy European bison (n = 206) were divided into the following age categories: (1) <1 year of age; (2) animals between 1 and 3 years of age; and (3) animals which have reached sexual maturity: (3a) animals between 4 and 8 years of age, (3b) animals between 9 and 15 years of age, and (3c) animals > 15 years of age. IgG was found to be predominant Ig in the serum regardless of the age of the animals. The significant positive correlation between IgG absolute and relative concentration and the age of animals was found. The absolute concentration of IgM did not differ significantly during the lifespan; however, the negative correlation was observed between percentage of IgM and European bison's age. IgA represented the least class of serum Ig. Total serum concentration of analyzed Ig also significantly increased with age. No gender-related differences were detected. Our findings represent a meaningful contribution to the studies on the immunity of European bison and effect of age on the immunoglobulin level. Our results would be useful for veterinarians and researchers in the studies with this animal's species.

Rates of erythropoiesis in mammals and their relationship with lifespan and hematopoietic stem cells aging

Investigations on possible links between hematological parameters and longevity are nearly absent. We tested the hypothesis that a fast rate of erythropoiesis, causing an earlier aging of the hematopoietic stem cells pool, contributes to a shorter lifespan. With this aim, we employed a new quantity, daily produced red blood cells per gram of body mass, as a measure of mass-specific rate of erythropoiesis. We found that among mammals rate of erythropoiesis and maximum lifespan are significantly correlated, independently from mass residuals. This seems to be confirmed also by intra-species comparisons and, although with limited data, by the significant correlation of rate of erythropoiesis and rate of telomere shortening in leukocytes (a proxy for hematopoietic stem cell telomere shortening). In our view, this may give a link of causality between rate of erythropoiesis and maximum lifespan. Further studies could test a similar hypothesis also for other kinds of stem cells.

Duration of antibody response following vaccination against feline immunodeficiency virus

Objectives Recently, two point-of-care (PoC) feline immunodeficiency virus (FIV) antibody test kits (Witness and Anigen Rapid) were reported as being able to differentiate FIV-vaccinated from FIV-infected cats at a single time point, irrespective of the gap between testing and last vaccination (0-7 years). The aim of the current study was to investigate systematically anti-FIV antibody production over time in response to the recommended primary FIV vaccination series. Methods First, residual plasma from the original study was tested using a laboratory-based ELISA to determine whether negative results with PoC testing were due to reduced as opposed to absent antibodies to gp40. Second, a prospective study was performed using immunologically naive client-owned kittens and cats given a primary FIV vaccination series using a commercially available inactivated whole cell/inactivated whole virus vaccine (Fel-O-Vax FIV, three subcutaneous injections at 4 week intervals) and tested systematically (up to 11 times) over 6 months, using four commercially available PoC FIV antibody kits (SNAP FIV/FeLV Combo [detects antibodies to p15/p24], Witness FeLV/FIV [gp40], Anigen Rapid FIV/FeLV [p24/gp40] and VetScan FeLV/FIV Rapid [p24]). Results The laboratory-based ELISA showed cats from the original study vaccinated within the previous 0-15 months had detectable levels of antibodies to gp40, despite testing negative with two kits that use gp40 as a capture antigen (Witness and Anigen Rapid kits). The prospective study showed that antibody testing with SNAP Combo and VetScan Rapid was positive in all cats 2 weeks after the second primary FIV vaccination, and remained positive for the duration of the study (12/12 and 10/12 cats positive, respectively). Antibody testing with Witness and Anigen Rapid was also positive in a high proportion of cats 2 weeks after the second primary FIV vaccination (8/12 and 7/12, respectively), but antibody levels declined below the level of detection in most cats (10/12) by 1 month after the third (final) primary FIV vaccination. All cats tested negative using Witness and Anigen Rapid 6 months after the third primary FIV vaccination. Conclusions and relevance This study has shown that a primary course of FIV vaccination does not interfere with FIV antibody testing in cats using Witness and Anigen Rapid, provided primary vaccination has not occurred within the previous 6 months. Consequently, Witness and Anigen Rapid antibody test kits can be used reliably to determine FIV infection status at the time of annual booster FIV vaccination to help detect 'vaccine breakthroughs' and in cats that have not received a primary course of FIV vaccination within the preceding 6 months. The duration of antibody response following annual booster FIV vaccination and the resulting effect on antibody testing using PoC kits needs to be determined by further research. The mechanism(s) for the variation in FIV antibody test kit performance remains unclear.

Curcumin attenuates the scurfy-induced immune disorder, a model of IPEX syndrome, with inhibiting Th1/Th2/Th17 responses in mice

BACKGROUND

Immunodysregulation polyendocrinopathy enteropathy X-linked syndrome (IPEX) is a lethal autoimmune disease caused by mutations in the Foxp3 gene scurfin (scurfy). Immunosuppressive therapy for IPEX patients has been generally ineffective and has caused severe side effects, however curcumin has shown immune regulation properties for inflammatory diseases, such as rheumatoid arthritis, psoriasis, and inflammatory bowel diseases without side effects.

OBJECTIVE

The aim of this study was to investigate whether curcumin would attenuate symptoms of IPEX in mouse model and would prolong its survival period.

METHODS

C57BL/6 mice were separated into scurfy or wild-type litter mate groups by genotyping, and each group subsequently was separated into 2 subgroups that were fed a 1% curcumin containing or normal diet from the last day of breast-feeding. After weaning, pups were fed either a 1% curcumin containing or normal diet until all scurfy mice die for survival data. To elucidate immune cell proportions in spleen and lymph nodes, cells were analyzed by flowcytometry. Cellular cytokine production was accessed to investigate the effects of curcumin in T cell differentiation in vitro.

RESULTS

Scurfy mice fed a 1% curcumin diet survived 4.0-fold longer compared to scurfy (92.5 days) mice fed a normal diet (23 days). A curcumin diet decreased all of the Th1/Th2/Th17 cell populations and attenuated diverse symptoms such as splenomegaly in scurfy mice. In vitro experiments showed that curcumin treatment directly decreased the Th1/Th2/Th17 cytokine production of IFN-γ, IL-4, and IL-17A in CD4⁺ T cells.

CONCLUSIONS

Curcumin diet attenuated the scurfy-induced immune disorder, a model of IPEX syndrome, by inhibiting Th1/Th2/Th17 responses in mice. These results have implications for improving clinical therapy for patients with IPEX and other T cell related autoimmune diseases.

Alterations with age in peripheral blood lymphocyte subpopulations and cytokine synthesis in beagles

Purpose

The immune system is considered to be affected by aging, which is linked to various immune pathogeneses. The purpose of this study was to determine age-associated changes in immune function of healthy dogs (beagles), specifically those of naive and memory T lymphocytes, based on cytokine synthesis.

Patients and methods

Blood samples were obtained from 44 healthy beagles that were divided into three age-groups: young (<4 years), middle-aged (4-8 years), and older dogs (>8 years). Subpopulations of T lymphocytes were determined by flow cytometry. Transcriptional (mRNA) levels of cytokines were determined for primary-cultured leukocytes using quantitative real-time polymerase chain reaction.

Results

There were negative correlations between dogs' ages and the number of peripheral blood mononuclear cells, T cells, and B cells. In particular, the number of naive CD4⁺ CD45RA⁺ T cells and CD8⁺ CD45RA⁺ T cells significantly decreased with age. The mRNA levels for interleukin (IL)-2, IL-2Rα, and interferon-gamma were significantly higher in young or middle-aged dogs (P < 0.05), whereas IL-4 mRNA expression was not significantly different over the different age-groups. IL-2Rγ mRNA expression tended to decrease with age.

Conclusion

Decreases of naive CD4⁺ and naive CD8⁺ T cells may be related to age-related immunosenescence in dogs. With regard to cytokine production, leukocyte IL-4 and IL-10 mRNA levels did not change with age, whereas IL-2, IL-2Rα, and IL-2Rγ mRNA levels decreased with age. These altered cytokine mRNA expression patterns may contribute to decreased naive T-cell function(s) with aging.

Immunophenotypical characterization in Andalusian horse: variations with age and gender

Assessment of lymphocyte subsets is an effective method for characterizing disorders such as leukemia, lymphomas, autoimmune and infectious diseases. In order to clinically interpret these parameters, normal reference values should be set, estimating age- and gender-related variations. This research aimed to: (1) characterize lymphocyte subpopulations in Andalusian horse, and (2) evaluate age and gender-related variations of lymphocyte subsets. Jugular blood samples were obtained from 159 animals, 77 males and 82 females, belonging to four age groups-1: 1-2 years (N=39; 21 males and 18 females), 2: 2-3 years (N=38; 16 males and 22 females), 3: 3-4 years (N=41; 19 males and 22 females) and 4: 4-7 years (N=41; 21 males and 20 females). T lymphocytes subsets were quantified by flow cytometry with monoclonal antibodies specific for CD2, CD4 and CD8 cell markers. B and NK cell counts were estimated by using a mathematical formula. No variations were found in T, B lymphocytes and NK cells between males and females. Animals of group 1 and 2 had a higher number of CD2, T, CD4+, CD8+, B lymphocytes and NK cells than animals of groups 3 and 4. The percentage of CD2 in group 1 was significantly lower than in group 4. The percentage of T and CD4+ lymphocytes in the group 1 were significantly higher than groups 2 and 3, respectively. Whereas the percentage of B cells calculated by flow cytometry was significantly lower in group 2 compared to group 4, the percentage of B cells calculated by a mathematical formula was higher in group 1. NK cells percentage was significantly lower in group 3 and 4 than in younger animals. In conclusion, in Andalusian horse, gender does not influence absolute numbers and percentages of T, B and NK. There is an age-related decline in absolute number of CD2, T, CD4+ and CD8+ lymphocytes, B lymphocytes and NK cells, with increasing percentage of CD2, T, CD4+ and B lymphocytes, and a decrease in NK with no differences in CD4/CD8 ratio. The decline of lymphocyte population numbers with age is a natural process in many animal species, and could be the origin for immune dysfunction observed in geriatric individuals.

Lymphoid organ development in rabbits: major lymphocyte subsets

Although rabbits represent an important animal model, little is known about the lymphoid organ development in this species. In the present study, lymphocyte subsets in peripheral blood, spleen, mesenteric and popliteal lymph nodes in newborn and 2-, 4-, 6- and 8-week old and adult were characterized. Lymphocyte subsets were detected using flow cytometry and monoclonal antibodies against rabbit CD4, CD8, T-cell-specific antigen and cross-reactive antibody against B-cell antigen CD79alpha. In neonates, lower numbers of T cells were detected in both peripheral blood and spleen than in mesenteric lymph nodes. In comparison with other compartments, CD79alpha(+) cells prevailed in the spleen. Post-natal development was characterized by a decreased CD4(+)/CD8(+) ratio due to increasing frequency of CD8(+) lymphocytes in all organs but mesenteric lymph nodes, where it was due to decreased numbers of CD4(+) lymphocytes. Another significant feature was the increase of B cells in peripheral blood and mesenteric lymph nodes.

The role of flow cytometry in companion animal diagnostic medicine

Flow cytometry is a powerful tool for characterising the composition of complex cell populations. The accuracy and precision of this technology for describing and enumerating cells exceeds traditional methods. The number of diagnostic veterinary laboratories with access to a dedicated machine is increasing, and there is the potential to offer a clinical flow cytometry service. The improved availability of monoclonal antibodies (mAb) to cell markers expressed by the leukocytes of companion animals, permits the implementation of comprehensive mAb panels suitable for diagnosis of lympho- and myeloproliferative disease. Reticulated erythrocyte and platelet quantification, antiglobulin assays for immune-mediated cytopenias, lymphocyte subset analysis, and immunophenotyping of lymphoma and leukemia, have been validated for companion animal samples on the flow cytometer. It is now timely to consider the role of flow cytometry in diagnostic practice, and the requirement for quality assurance and standardization of testing procedures.

Age-related alterations to immune parameters in Labrador retriever dogs

In order to assess age-related changes in the immune status of Labrador retriever dogs, leukocyte phenotypes, lymphocyte proliferative capacity, and serum antibody levels were measured in four cohorts of dogs, ranging from 2 to 10 years of age. Absolute numbers of white blood cells, lymphocytes, monocytes, granulocytes, and CD3+, CD4+, CD8+ and CD21+ lymphocytes significantly decreased with increasing age. Relative percentages of lymphocytes and CD4 cells were significantly decreased, and relative percentages of granulocytes and CD8 cells significantly increased, with age. The CD4:CD8 ratio showed a significant age-related decrease. Proliferative responses of T-cells to mitogens in whole-blood cultures either increased (Concanavalin A) or remained the same (phytohemagglutinin) with age when data was normalised to allow for differences in responding cell number. Similarly, normalised data of proliferative response to anti-CD3 stimulation together with phorbol 12-myristate 13-acetate showed an age-related increase. Serum levels of total IgA significantly increased with age whereas total IgG levels remained unchanged. These observations illustrate a significant change to a number of immune parameters with age. However, further work is required to determine whether the differences reported here are sufficient to cause overt or functional immune senescence in Labrador retriever dogs.

Lymphatic organ development in dogs: major lymphocyte subsets and activity

In the present study, we have characterized lymphocyte subsets and activity in peripheral blood, spleen, mesenteric and popliteal lymph nodes in pups from birth till the age of one month and compared the results with the situation in the group of three adult dogs. In neonatal pups, lower numbers of CD3(+) T-cells were detected in both the spleen and peripheral blood than in lymph nodes. In contrast to the other compartments, CD21(+) B-cells prevailed in the spleen, which resulted in low values (<1) of the CD3(+)/CD21(+) ratio. Low numbers of CD8(+) lymphocytes were characteristic in all compartments immediately after birth; consequently a high CD4(+)/CD8(+) ratio has been calculated. Postnatal development was characterized by an increasing frequency of CD8(+) lymphocytes in all organs studied. Another typical feature of the early period of life was a relative decrease of B-cell numbers, which was compensated by an increasing proportion of T-lymphocytes, particularly in the peripheral blood and spleen. DNA synthesis in newborn pups' cells as measured by in vitro thymidine incorporation was surprisingly high in non-stimulated control samples, notably in the spleen. Further development of lymphocyte activity was characterized by the decline in spontaneous activity in all organs. Stimulation indices upon mitogen-induced proliferation increased proportionally to the decrease in spontaneous activity. Based on our experimental data, we have concluded that pups are born with a relatively competent immune system the structure of which, however, markedly develops during a few postnatal weeks.

Age-related differences in parameters of feline immune status

In order to assess age-related differences in feline immune status, 101 domestic short haired cats were assigned to two groups, adult (2-5 years, n=50) and senior (10-14 years, n=51). Analyses of leucocyte populations, lymphocyte subsets, complement activity, serum immunoglobulins and acute-phase proteins were undertaken and revealed significant differences between the two groups. The senior group had significantly lower WBC, lymphocyte and eosinophil counts than the adult group. Neutrophil, monocyte and basophil counts did not differ between the groups. Flow cytometry analysis, in combination with differential WBC data, revealed that the absolute values (cells/l) of T-cells, B-cells and natural killer (NK) cells were significantly lower in the older animals. While serum immunoglobulins IgA and IgM were higher in the senior group when compared with the adult group, no significant differences were observed in complement activity or in serum acute-phase proteins. Our findings suggest that age-related changes to parameters of immune status in the feline model are likely to follow a similar pattern to those observed in other long-lived mammalian species.

Regulation of dendritic cell expansion in aged athymic nude mice by FLT3 ligand

This report describes age-related alterations of dendritic cells (DC) distribution in nude athymic mice in vivo and reversal of certain age-dependent defects by an in vivo administration of hematopoietic growth factor FLT3 ligand (FLT3L). There are decreased percentages of CD11c(+) DC in the bone marrow and spleen and a reduced expression of MHC class II and CD86 molecules on DC in old nude mice. The decreased levels of CD11c(+) DC were due to the CD8alpha(-) DC subset. The distribution of CD11c(+) CD8alpha(+) DC in the lymphoid tissues was not different in young and old mice. The effect of in vivo administration of FLT3L on the generation and distribution of DC in the lymphoid tissues in young and old nude mice was also evaluated. Although, FLT3L had a higher inductive potential on the expansion of DC from the bone marrow in the elderly mice, the total level of CD11c(+) DC in the young animals was still significantly higher as compared to the old animals. Interestingly, FLT3L induced a pronounced redistribution and accumulation of MHC class II(+) DC in the lymphoid tissues in old mice, markedly increased the accumulation of CD8alpha(-) DC in the bone marrow in both young and old nude mice, and elevated both CD8alpha(-) and CD8alpha(+) DC in the spleen in young mice. However, only the level of CD8alpha(+) DC was up regulated in the spleen in old athymic mice after FLT3L-based therapy. In summary, abnormalities in DC generation and distribution in old athymic mice could be, in part, circumvented by the in vivo administration of FLT3L.